In providing electronic instrumentation, it is frequently necessary to apply a signal from a signal source, such as a sensor or transducer, to electronic signal processing circuitry while maintaining complete electrical isolation between the signal source and the signal processing electronics. Various methods are presently used in constructing such isolation amplifiers, including transformer coupling and photoelectric coupling of the input and output circuits.
One problem with previous transformer-coupled isolation amplifiers has been non-linearity in the amplifiers due to partial saturation of the transformer core with varying input signal levels. In designing such transformer-coupled amplfiers, typically one must make a trade-off between limited dynamic range and non-linearity arising from the non-linear BH curve of a transformer as signal levels increase.